Information Notice No. 85-35: Failure of Air Check Valves to Seat

SSINS No.: 6835
IN 85-35
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
April 30, 1985
Information Notice No. 85-35: FAILURE OF AIR CHECK VALVES TO SEAT
Addressees
All nuclear power reactor facilities holding an operating license (OL) or a
construction permit (CP).
Purpose:
This information notice is being provided as a notification of a potentially
significant problem pertaining to Parker-Hannifin Corporation check valves,
supplied by Anchor/Darling Valve Company, that may degrade the capability
for closing main steam isolation valves (MSIVs) or feed water isolation
valves (FWIVs) or may inhibit other safety functions. It is expected that
recipients will review the information for applicability to their facilities
and consider actions, if appropriate, to preclude a similar problem
occurring at their facilities. However, suggestions contained in this
information notice do not constitute NRC requirements; therefore, no
specific action or written response is required.
Description of Circumstances:
On March 14, 1985, at Byron Unit 1, two MSIVS failed to close on a main
steam line isolation signal as required. The cause was determined to be
failure of instrument air check valves to seat in response to gradually
decreasing air pressure.
At the time of the isolation signal, the unit was cooling down following the
startup test for loss of offsite power. The removal of offsite power had
deenergized the station air compressors, allowing the instrument air
pressure to decrease. The leaking instrument air check valves had allowed
air accumulators to bleed down, removing the air pressure needed to shift
hydraulic spool valves so that the hydraulic circuits could close the MSIV
(see Figure 1). As a result, one of the four MSIVs did not close and one
MSIV only partially closed.
In subsequent bench testing, 7 of 8 check valves removed from Unit 1 failed
to seat, as did 4 of 11 replacement valves, when gradual loss of instrument
air pressure was simulated. All valves seated when the supply pressure was
rapidly decreased. Preoperational testing using rapid depressurization was
satisfactory; however, preoperational testing did not require slow
depressurization. Subsequent retesting has indicated continuing problems.
The licensee has decided to replace all these Parker-Hannifin check valves
with Parker-Hannifin check valves of modified design.
8504250455
.
IN 85-35
April 30, 1985
Page 2 of 2
The valves that leaked are identified in Parker-Hannifin literature as
"Barstock Inline Check Valves, C Series, Catalog 2502." They were
manufactured by Parker-Hannifin and supplied by Anchor/Darling Valve Company
(Part No. W30261). The replacement valves are described as Viton Seat Body
Brass Check Valves with order number 8F-CAL-10-B. Anchor/Darling has
notified the NRC that the same check valves have been supplied to the plants
listed in Attachment 1 for use in instrument air supply lines to MSIV
actuators or to FWIV actuators. It should also be noted that the valves may
be in use in other applications and/or other facilities.
A previous Information Notice, 82-25, described a related event with
different equipment. Valves equipped with Ralph A. Hiller Co. actuators were
capable of achieving their fail-safe position when the instrument air header
was suddenly depressurized, but would not do so with a slow
depressurization.
No specific action or written response is required by this information
notice. If you have any questions about this matter, please contact the
Regional Administrator of the appropriate regional office or this office.
Edward L. Jordan, Director
Division of Emergency Preparedness
and Engineering Response
Office of Inspection and Enforcement
Technical Contact: Vern Hodge, IE
301-492-7275
Attachments:
1. Figure 1 MSIV Control System
2. List of Known Applications
3. List of Recently Issued IE Information Notices